Dual push button control system



Nov. 29, 1960 H. L. RAYMOND DUAL PUSH BUTTON CONTROL SYSTEM Filed Juhe24, 1955 mend INVENTOR ATTORN United States Patent DUAL PUSH BUTTONCONTROL SYSTEM Henry L. Raymond, Shelton, Conn., assignor to DictaphoneCorporation, Bridgeport, Conn., a corporation of New York Filed June 24,1955, Ser. No. 517,695

9 Claims. (Cl. 317-135) This invention relates to an electrical controlsystem for the dual push button operation of machine tools.

An object of this invention is to provide an electrical system for thedual push button operation of a machine which will require that theoperator in order to start the machine must depress simultaneously orwithin a brief interval each push button.

A better understanding of the invention, together with a fullappreciation of its many advantages, will best be gained in thefollowing detailed description given in connection with the accompanyingdrawings in which:

Figure 1 is a perspective view of a typical machine tool showing thelocation of push buttons;

Figure 2 is a circuit drawing of the basic push button control system;and

Figure 3 is a circuit drawing of a modified dual push button controlsystem.

Referring now to Figure 1, the dual push buttons generally indicated at2 and 4 are shown on machine 6 and are so arranged that the operatormust clear his hands from the work 8 and away from the travel 10 of theoperating part of the machine in order to press the buttons. The pushbuttons 2 and 4 are located on the machine convenient to the operator.Figure 1 generally depicts this invention as attached to a machine wherecontrol box 12, control wires 14 and 16 and push buttons 2 and 4 showthe general arrangement of the control system. Leading from the top ofthe control box 12 are control wires, not shown, which lead to the maincontactor or pneumatic relay which actuates the machine. The maincontactor or pneumatic relay (see Figs. 2 and 3) is generally indicatedby power device 22.

Figures 2 and 3 illustrate two arrangements of the control system.

Referring particularly to Figure 2, one embodiment of a safety controlsystem incorporating the present invention is illustrated as comprisinga source of power, usually at 110 volts A.C., shown as conductors 18 and20 from a power house. The circuit diagram in Figure 2 illustrates theposition of the devices when power is applied to leads 18 and 20 butbefore the push buttons 2 and 4 have been pressed to start the machine.Each push button 2 and 4 as illustrated constitutes the movable pole ofa single pole double throw switch normally biased to one position andmanually operable to another position. The system illustrated in Figure2 comprises two push buttons, 2 and 4, and switches operated thereby, atime delay relay 21 and a power device 22. These ele-.

ments of the electrical system are arranged in series across power lines18 and 20 so that power device 22 will be energized when the circuit iscomplete. More specifically the circuit comprises push button switch 2,contact 24, wire 28, power device 22, wire 30, contact 33, safety switch32 of relay 21, wire 34, contact 26 and push button switch 4. In theoperation of this circuit push buttons 2 and 4 are closed against theirrespective contacts 24 and 26 completing the electrical circuit throughpower device 22, this energizes power device 2,962,633 Patented Nov. 29,1960 "ice 2 22 and thereby starts machine 6. The single pole doublethrow switches or push buttons 2 and 4 are permanently biased in oneposition but are manually operable to the other position, which may behereinafter referred to as the normally closed and normally openedpositions respectively. The circuit through the push buttons to thepower device is complete only so long as safety switch 32 remains closedagainst contact 33 and push buttons 2 and 4 are held against contacts 24and 26 respectively.

It can be seen from Figure 2 that time delay relay 21 is normallyenergized directly from the power line through normally closed contacts35 and 36 when the push buttons 2 and 4 are in their biased position.The power thus flows through the solenoid coil energizing of relay 21.Figure 2 shows the position of safety switch 32 when time delay relay 21is energized as above described. In energizing relay 21, the currentflows through rectifier 38, resistor 40 to D.C. solenoid 42 and thenceto the switch operated by push button 2 by wire 43 and contact 35.

When either push button 2 or 4 is depressed to close the normally opencircuit at 24 and 26 to energize power device 22, the circuit supplypower to solenoid 4-2 of relay 21 is opened and the solenoid 42 would nolonger be energized except for the energy stored in condenser 44 whichcontinues to supply, for a short time through resistance 40, D.C.solenoid 42. This arrangement of rectifier 38, resistance 40, solenoid42 and condenser 44 forms a time delay circuit which continues toenergize solenoid 42 holding safety switch 32 of relay 21 closed for ashort time after the power from the line to relay 21 is interrupted. Inthe present embodiment resistance and capacitor values were selected togive approximately one-half second time delay.

In the operation of this circuit if push buttons 2 and 4 are pressed atthe same time the circuit through power device 22 is complete and thetiming cycle of relay 21 commences. Since the power to device 22 issupplied for a full half-second before switch 32 opens interrupting thesupply of power, device 22 will be energized and machine 6 will bestarted.

If however, push buttons 2 and 4 are depressed one after the other thetiming cycle of relay 21 will begin at the moment the first button ispressed, interrupting the supply of power to solenoid 42, while device22 will not begin to be energized unless the second button is pressed tocomplete the circuit through device 22 before the expiration of the timedelay of relay 21.

Accordingly, if the delay between the pressing of push buttons 2 and 4exceeds the time delay cycle set for the operation of relay 21, powerdevice 22 will not be energized because safety switch 32 will open andthe circuit through device 22 will not be complete. Further whatevertime delay occurs between the pressing of the first and second pushbuttons, this time will in effect have to be subtracted from the timedelay cycle of relay 21 in order to determine the time current quantityof power to device 22. Therefore if there is delay between depressingone push button and the pressing of the other there may not be asufficient quantity of current fully to energize device 22 and machine 6will not start.

If push button 2 has been permanently jammed to the start position,power device 22 will not operate upon the pressing of push button 4because safety switch 32 will be open, its short time delay havingpreviously ex pired. The operation of the time delay relay 21 requiresthat push buttons 2 and 4 be pressed simultaneously or in rapid sequenceand released each time before beginning another cycle.

In the circuit illustrated in Figure 2 the capacitor and resistor havebeen selected so that the maximum length of time for current to flowthrough power device 22 is approximately one-half second. If this is notlong enough for the solenoid in power device 22 to become energized thenthe machine will not operate; similarly if the power device must remainenergized for a brief time to permit the complete transfer of energy tothe working part of the machine, an operation for a shorter time will beonly partially effective. While the time delay of solenoid 42, in Figure2, may be extended by changing the value of capacitor 44 and resistance40 there is a practical limit to such modification.

Referring now to the circuit illustrated in Figure 3 there is shown onemethod by which this time may be extended so that power device 22 willbe fully energized and remain so energized sufficiently long so that thetransfer of energy may effectively be completed.

The circuit shown in Figure 3 shows the devices before the operatorpresses push buttons 2 and 4 and with power supplied to lead lines 50and 52. A first time delay relay 54 is thereby normally energized and asecond time delay relay 56 is normally deenergized. First relay 54 isenergized from line 50 through push button contact point 55, controlwire 58, rectifier 60 and resistor 62, solenoid 64, control wire 66,push button contact 68 to line 52. First and second line switches 70 and72 close against contacts 71 and 73 of first time delay relay 54 whenrelay 54 is energized thereby supplying power through switch 70 andcontact 71 to resistor 75 and lighting indicating lamp 77. Theindicating lamp shows visible evidence that the system is reset andready to operate power device 22 after push buttons 2 and 4 are pressed.

If push buttons 2 and 4 are pressed simultaneously or'substantially sothe electrical circuit to power device 22 is complete through contactpoint 78, control wire '80, second line switch 72, control wires 74 and76 to power device 22 and through control wires 82 and 84 to contact 86and line 52.

By pressing either push button 2 or 4 the circuit through solenoid 64 offirst relay 54 is opened initiating the the one-half second or lessprovided by first relay 54.

The time delay between the sequence operation of the push buttons mustbe subtracted from the effective time in which current will flow topower device 22, because the time delay of first relay 54 is measuredfrom the beginning of the time either push button 2 or 4 is pressed.Therefore in the case of a large time-current demand for power device22, it is possible that the timing circuit through second line switch 72will open before power device 22 is fully energized thereby preventingthe effective operation of the machine.

The modified circuit illustrated in Figure 3 is arranged to compensatefor the time delay in the sequence operation when push buttons 2 and 4are pressed. I have shown above how the circuit in Figure 3 is similarto the circuit in Figure 2 and I have discussed one phase of theoperation of the circuit illustrated in Figure 3.

The circuit set forth in Figure 3 permits a greater time delay betweenthe sequence operation of push buttons 2 and 4 without reducing theeffective current flow to power device 22. This is accomplished by adual timedelay system, one time delay means to limit the time withinwhich both push buttons must be pressed, a second time delay means whichaccurately times the flow of current to power device 22 so as to assureits operation and yet limits the flow of current to power device 22 sothat only a single operation is possible.

Referring again to Figure 3 it is seen that with push buttons 2 and 4closed against normally opened contacts 86 and 78, power is applied topower device 22 through second line switch 72 but first relay 54immediately begins to time-out. Power to second time delay relay 56 issupplied through second line switch 72, contact 73, wire 74, wire 76 tocondenser 88, rectifier through solenoid 92, to wires 82, 84 and contact86 to line 52. As second relay 56 picks up first relay 54 drops outalmost at once because the circulating current through resistor 62 andcondenser 94 is short circuited by wire 96, resistor 98, through firstcontrol switch 99, contact 100, wires 102, and 66 to condenser 94,thereby causing relay 54 to drop out. Power is supplied to solenoid 92of second relay 56 by the circuit through push 'button contact 78, wire80, contact 106, second control switch 107, wires 74 and 76 to condenser88 and rectifier 90. As relay 56 remains energized, power is supplied topower device 22 by circuit from push button contact 78, through wire 80,contact 106, second control switch 187, wires 74 and 76 to power device22, through wires 82 and 84 to push button contact 86.

Flow of current to solenoid 92 begins to decrease as condenser 38becomes charged and when the current through solenoid 92 becomes toosmall to effectively energize the solenoid, second relay 56 will dropout thereby opening the circuit at second control switch 107. Condenser88 is short circuited through wire 188, resistor 110, wire 112, contact114 second control switch 107, wires 74 and 76 thereby dischargingcondenser and preparing it for another time cycle. Second control switch107 of second relay 56 is a double throw switch so arranged as tocomplete the shorting circuit to contact 114 when second relay isdeenergized and said second control switch is in a normally closedposition. When second time delay relay 56 is deenergized, second controlswitch 107 is in a normally open position with respect to a pathparallel to second line switch 72. In order to assure the complete timesequence operation of the entire circuit shown in Figure 3 push buttons2 and 4 must continuously be pressed, if either push button is releasedthe main circuit is opened and the sequencing operation of relays 54 and56 is interrupted. Further, after the cycle is complete both pushbuttons must be released in order to energize relay 54, which is alsoshown by the visual indicator neon light 77. When this light glows the'push buttons may again be pressed for another operation of the machine.

The above description is intended to be illustrative of the invention.Various changes in the circuit described may occur to those skilled inthe art and these may be without departing from the spirit and scope ofthe invention as set forth.

I claim:

1. A safety control system in an electric circuit of an electricstarting device for operating a machine through a single cycle onlywhich control system protects both hands of the machine operator andcomprises power lines, a first branch circuit having a relay winding, asecond branch circuit having a safety switch operated by the relaywinding in the first branch circuit and an electric responsive devicefor initiating operation of the machine, a pair of manually operablecurrent control devices each connected to one of the power lines and thedevices being spaced so that both hands must be used to operate thecontrol devices "substantially simultaneously, each current controldevice having a current directing means biased to connect the firstbranch circuit between the power lines to normally energize the relaywinding therein and close the safety switch in the second branchcircuit, each current control device being operable by the presence ofa-hand of the operator to disconnect the first is branch circuit fromits power line and connect the latter to the second branch circuit, anda tinting device connected to delay the opening of the safety switch fora predetermined time after the first branch circuit is opened by eitherof the pair of control devices operated by the presence of a hand andless than the time required for the machine to operate through a cyclewhereby operation of the machine is initiated only when the secondbranch 'circuit is energized by the presence of both hands on thecurrent control devices, the safety switch is opened to tie-energize thesecond branch before the machine completes a cycle and the safety switchis closed only when both hands are removed from the current controldevices.

, 2. A safety control system in an electric circuit for an electricresponsive device to operate a machine cyclically which protects bothhands of the machine operator comprising power lines, a first branchcircuit having a relay winding and an electric time control for delayingdeenergization of the winding for a predetermined period of time afterthe branch circuit is opened, a second independent branch circuit havinga safety switch operated by the relay winding in the first branch and anelectric responsive device for initiating operation of the machineconnected in series with the safety switch, a pair of manually operablesingle-pole, double-throw switches, each having its pole connected toone of the power lines, respectively, and so spaced that both hands mustbe used to operate the switches simultaneously, the poles of theswitches being biased to connect the first branch circuit between thepower lines to normally energize the relay winding therein and close thesafety switch in the second branch circuit, each of the single-pole,doublethrow switches being operable by one hand of the operator todisconnect its power line from the first branch and connect it to thesecond branch circuit whereby both control switches must be manuallyoperated within the predetermined time period of the electric timecontrol in the first branch circuit to initiate operation of the machineand the safety switch in the second branch circuit is opened at the endof said predetermined period of time to limit operation of the machinethrough a single cycle.

3. In an electric safety control system for a power operated machinewhich requires the use of both hands of the attendant during operationof the machine comprising an electric responsive device for controllingoperation of the machine, a source of electric power having a pair ofconductors, an electric branch circuit for connecting the electricresponsive device between the conductors of the source of power, saidcircuit including a pair of switches each comprising normally engagedcontacts and other contacts engaged when the switch is manually operatedto close the circuit to the electric responsive device, each switchbeing connected to one side of the power line, a safety switch in saidbranch circuit connected in series with the electric responsive devicebetween said pair of switches, a direct current relay for closing thesafety switch, a second branch circuit having a rectifier for connectingthe relay between the conductors of the electric power source when thecontacts of the pair of switches are normally engaged, a timing devicefor opening the closed safety switch after a period of time less thanrequired for the machine to operate through a cycle comprising the coilof said relay and a resistance condenser system in said second branch todelay opening of said safety switch a predetermined period of time aftermanual operation of one and both of said manually operated switches, acontrol switch in parallel with said safety switch, means responsive tothe closing of said branch circuit to the electric responsive device forclosing said control switch, a second timing device for opening saidcontrol switch after a predetermined period of time and said secondtiming device being responsive to and initiated by actuation of saidcontrol switch.

4. An electric control system for insuring the safe operation of acyclically operated machine which is ins herently dangerous to the handsof the attendant com prising an electrically responsive device forcontrolling operation of the machine through a cycle, a source of power,a switch operating means, an electric circuit comprising a first branchfor connecting said source of power to the electric responsive deviceand a second branch arranged in parallel with said first branch forconnecting the source of power to the switch operating means, a

safety switch in said first branch connected for opera tion to closedposition by the switch operating means in the second branch, a pair oftwo position switches having contacts normally engaged to energize thesecond branch and other contacts engaged when the switches are manu+ally operated to de-energize the second branch and energize the firstbranch, a timing delay means in the second branch to maintain the switchoperating means energized and thereby hold said safety switch closed fora predev termined period of time after said second branch isdeenergized, a second switch connected in parallel with said safetyswitch in the first branch for connecting said source of power to theelectric responsive device of said machine, switch operating means toclose and to open said second switch, said switch operating means beingconnected to the first branch for energization therewith, and anelectrically operated timing means connected to the first branch and theswitch operating means to delay the opening of said second switch for apredetermined period of time after the safety switch is opened.

5. A control system comprising, a power device,-an indicating lamp, twopush button switches, each switch having contacts normally engaged tocomplete one circuit and a contact engaged when the switch is manuallyoperated to complete another circuit, two time delay relays each havinga DC. solenoid and two separate contactors, conductors connecting one ofsaid relays in one branch circuit, a first time delay system connectedin said one branch circuit to operate with the time delay relay therein,said system comprising a rectifier, condenser and resistor, conductorsconnecting the other relay in another branch circuit, a second timedelay system connected in said other branch circuit to operate with thetime delay relay therein, said second system comprising two condensersand a rectifier, a contactor of said one relay being connected tocontrol the power device and lamp, respectively, a shorting resistancefor each of the first and second time delay relays, and said shortingresistances being connected to be operated in reverse order by theseparate contactors of the second relay.

6. A safety control system for a power operated machine which insuresthe removal of the hands of the attendant during operation of themachine including a power supply, a control circuit and a device to beoperated, said control circuit comprising two push button switches witheach having one normally open and one normally closed contact, a firstand second relay each having a DC. solenoid and a first and secondcontacter, a first time delay system to operate with said first relay,said system comprising a rectifier, condenser and resistor, a secondtime delay system to operate with said second relay, said second systemcomprising two condensers and a rectifier, an indicating lamp in serieswith the first contacter of said first relay and connected to said powersupply to signal when the control circuit is ready for operation, saidnormally closed contacts of said push button switches being connected inseries with said solenoid of said first relay whereby said relay isnormally energized, said normally open contacts of said push buttonswitches being connected in series with the second contacter of thefirst relay, and said power operated device and said first contacter ofsaid second relay being connected in parallel with the second contacterof the first relay whereby said power operated device can be fullyenergized when contacts of said first relay are opened, and said secondtime delay system operating to 7 open :the first contact of the secondrelay after the time period-of said system has'expired to 'open thecircuit to the power operated device.

7. A safety control system for a power operated'rnachine comprising afirst single-pole double-throw switch having 'a pole normally engagingone contact and manuallyoperable to engage a second contact, a secondsinglepole double-throw switch having a pole normally engaging'onecontact and manually operable into engagement with'a second contact, an'electric power operated device for controlling operation ofthermachine, a safety switch having normally open contacts and asolenoid operable when energized to close the contacts, power linesconnected to thepoles of the first and second single-pole double-throwswitches, a branch circuit having conductors connecting the safety"switch solenoid to the normally engaged contacts of the pair ofsingle-pole double-throw switches to complete a circuit through thesolenoid to hold the safety switch in closed position, a branch circuitconnecting the s'afety'switch and electrically operated power device inseries between the second mentioned contacts of the pair of single-poledouble-throw-switches to'complete a circuit through the power devicewhen the poles of both switches are manually operated into engagementwith the second contacts, electrically operated time delay means fordelaying the opening of the safety switch for a predetermined period oftime after the pole piece of either-single-pole double-throw switch ismanually operated to open the branch circuit, said electrically operatedtime delay means being connected acrosssaid power line in series with'said fi'rst and second switches so that said series circuitacross saidpower line is com- 'pleted when the poles ofsaid first and secondsingle-pole double-throw switches are-in the normal engaged positionwith the first mentioned-contacts and said time delay means is energizedthereby holding said safety switch 'closed, relay means interconnectedwith said first time delay means and said power lines comprising asecond interrupting switch connected in parallel with the safety switchin the second mentioned branch circuit for energizing the power device,a solenoid for operating the second interrupting switch to closedposition and connected in the second mentioned branch circuit forenergization therewith, and a second electrical time delay meansconnected to delay the de-energization of the solenoid and opening ofthe second interrupting switch for a prede termined period of time afterthe safety switch opens.

8. A control system as claimed in claim 7 in further combination with asecond relay means operated by the safety switch solenoid, an indicatinglight arranged in a circuit controlled by the relay means so that saidindicating light will unfailingly show when power is on and also whensaid first time delay means is energized Where by the control system isready to operate.

9. A control system as claimed in claim 7 in which said second timedelay means includes a condenser, rectifier and DC. solenoid connectedfor energization by closure of a circuit through the power device.

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